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From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: SLIP documents
Message-ID: <5847@auspex.auspex.com>
Date: 11 Feb 91 00:32:20 GMT
References: <1991Feb8.203703.25654@zoo.toronto.edu> <84702@sgi.sgi.com> <1991Feb9.051623.29415@Think.COM>
Organization: Auspex Systems, Santa Clara
Lines: 30

>It isn't NFS that uses unchecksummed UDP, it's SunOS (or maybe BSD Unix) in
>general (in its default configuration).  In fact, SunOS doesn't provide a
>way for a UDP-based application protocol to control whether it uses
>checksums -- it's a single, system-wide parameter.  Even worse, this one
>parameter controls both whether checksums are generated during sending and
>whether they are checked when receiving.

The latter two statements are true of BSD, as it comes from Berkeley,
from 4.3BSD to 4.3-reno.  Whether UDP checksumming is enabled or not in
BSD as it comes from Berkeley is, by default, under the control of the
COMPAT_42 #define; that doesn't seem to be on in most of the
configuration files, so I don't think the first statement is true of
BSD, although it is true of SunOS (SunOS != BSD).

>>				Ours do.  I'm told that Sun's does as
>>of the NFS 3.2 source release.
>
>Since the socket library doesn't provide a way to enable or disable UDP
>checksums (I could be wrong -- I simply searched for "checksum" in the
>setsockopt man page), I don't see how the NFS source release can do this.

It can if the default configuration of the NFS source release turns the
system-wide parameter on; he didn't say the NFS 3.2 source release lets
you arbitrary control whether UDP checksumming is done, he just said
that he was told that it *DID* UDP checksumming as of the NFS 3.2 source
release.

The NFS 4.0 source release is derived from 4.3BSD, and behaves like
4.3BSD in this regard - "udpcksum" is turned on only if COMPAT_42 is
defined, and it's not defined in the GENERIC configuration file.